Sling



FIG. 1 is a perspective view of the sling showing my new design;

FIG. 2 is a rear view thereof; and,

FIG. 3 is another perspective view, showing the design in use.

The broken lines showing of environment in the drawings is included for the purpose of illustrating only and forms no part of the claimed design. 

The ornamental design for a sling, as shown and described. 